If $a + b = -1$ and $x + y = -3$, what is $-10b - 10a - x - y$ ?
$= -10a - 10b - x - y$ $= (-10) \cdot (a + b) + (-1) \cdot (x + y)$ $= (-10) \cdot (-1) + (-1) \cdot (-3)$ $= 10 + 3$ $= 13$